A combination of a worm and a worm gear used in a regular machine is shown as an example of a gear in FIG. 18. A spur gear placed with the axis of rotation thereof set perpendicular to its base plate surface as shown in FIG. 17, and provided with projections on a circumferential surface thereof has a shape easily formed by the film formation techniques and fine processing techniques used in a related art semiconductor process. However, a gear other than such spur a gear and having a complicated shape, for example, a gear having helical teeth, such as a worm is not being manufactured.
A gear having magnetic teeth instead of projection type teeth on a circumferential surface thereof is proposed in Japanese Patent Laid-Open No. 56146/1997. The magnetic teeth of this kind of gear are formed on a flexible base plate by using a semiconductor process separately from a gear base. The flexible base plate on which the magnetic teeth are formed is thereafter wound around a gear base to complete a magnetic gear. However, according to this method, gears of sizes in the order of up to around millimeter can be manufactured but it is difficult to manufacture gears of sizes in the order of micron and submicron.
A driving actuator (motor) to be incorporated in a micromachine demands to be microminiaturized. A microminiaturized actuator generates a low power. In order to operate a micromachine with a low generated power, it is necessary that power transmission gearing having a high reduction ratio be provided in its power transmission path. The above-mentioned gears, i.e. a gear having projections on a circumferential surface thereof, a gear with magnetic teeth formed on a circumferential surface thereof and a gear with electrostatic teeth formed on a circumferential surface thereof are effectively used for this gearing.
The present invention provides gears mentioned above and formed on various base plates, such as a silicon base plate, a glass base plate, a ceramic base plate, a plastic base plate, a metal base plate and the like.
The gears to which the present invention is applied are a gear capable of being formed on a front surface and a rear surface and in an inner portion of a base plate, having projections on a circumferential surface thereof and rotated with other gear meshed therewith, or a magnetic gear rotated by a magnetic force, or an electrostatic gear rotated by an electrostatic force. In the case of the spur gear shown in FIG. 15, the gear is formed of a complicatedly shaped gear, for example, a helically shaped worm shown in FIGS. 1 and 2, a spur gear shown in FIG. 7 the axis of rotation of which is parallel to a base plate surface, a spur gear the axis of rotation of which is inclined, a bevel gear shown in FIG. 9 and an inclined bevel gear, etc., which are other than a spur gear the axis of rotation of which is parallel to a base plate surface, and these complicatedly shaped gears are indispensable to the practical utilization of a micromachine.
The present invention has been made in view of these points, and provides worms the axes of rotation of which are perpendicular, inclined and horizontal with respect to base plates thereof, spur gears the axes of rotation of which are horizontal and inclined with respect to base plates thereof, and bevel gears the axes of rotation of which are inclined, perpendicular and horizontal with respect to base plates thereof on all of which teeth of one of a gear having projections on a circumferential surface thereof, a gear having magnetic teeth on a circumferential surface thereof and a gear having electrostatic teeth on a circumferential surface thereof, which could be microminiaturized as gears for transmitting power to a micromachine, are provided by making use of the film formation techniques and fine processing techniques used in a semiconductor process; and a method of manufacturing these gears.